Support quiet mode

[Quintus]

Hi there,

I just thought it might be useful to implement a -q or --quiet switch that turns off all output except for errors. I intend to run greg from cron, so while I could just redirect the standard output to /dev/null I think a specific switch for this seems more "clean". Most other downloading programs like wget (-q) or curl (-s) have such a switch, too.

Vale, Quintus

[manolomartinez]

This should be easy, and useful. I'll get to it as soon as I can. Manolo